py3: make localrepo filtered repo cache work on py3

I don't know if this is the right fix, but it makes
test-py3-commands.t pass again.

Differential Revision: https://phab.mercurial-scm.org/D56

mercurial/localrepo.py

@@ -553,7 +553,7 b' class localrepository(object):'
             # class of this repo. Give it a name containing the
             # filter name to aid debugging.
             bases = (repoview.repoview, key)
-            cls = type('%sfilteredrepo' % name, bases, {})
+            cls = type(r'%sfilteredrepo' % name, bases, {})
             self._filteredrepotypes[key] = cls
 
         return self._filteredrepotypes[key](self, name)